In recent years, a fiber to the home (FTTH) system is provided so as to provide various information including broadcast and communication information by connecting an optical fiber to ordinary homes. The system is widely installed in an apartment and a house. In the above mentioned FTTH system, an optical fiber is connected to a home in such a way that the ends of the optical fiber are finished with an optical fiber connector. Here, a FTTH worker prolongs an optical fiber up to a home by setting the optical fiber a couple of meters longer than an actually needed length in consideration of the connection between the optical fibers. In addition, the worker cuts an optical fiber by the length that is needed for a corresponding home which becomes an on-site location, and assembles an optical fiber connector at each end of the optical fiber, and the assembled optical fiber connector is connected to an optical adaptor and is finally installed at the home.
Various technologies on the above-mentioned optical fiber connector to connected to the optical fiber connector are described in the following patent documents: Korean patent registration publication number 10-0669947; Korean patent publication number 10-2009-0078350; Korean patent publication number 10-2009-0083373; Korean paten publication number 10-2007-0045972; Japanese patent publication number Hei 2009-69607; Japanese patent publication number Hei 2008-225461; and Korean patent registration number 10-1038195.
When connecting the ends of the ferrule optical fiber installed at the ferrule with an adhesive and the ends of the main optical fiber, the conventional optical fiber connector is connected by a mechanical connection method which uses a main cable alignment member configured to accommodate the ends of the ferrule optical fiber and the ends of the main optical fiber as disclosed in the in-site assembling type optical fiber connector of Korean patent registration publication number 10-0669947 or a melted connection method which reinforces the melted connection part with a reinforcing sleeve formed of a shrinkable tube after the ends of the ferrule optical fiber and the ends of the main optical fiber are melted and connected using an optical fiber melting connector (refer to Korean patent publication number 10-2009-0083373; Korean paten publication number 10-2007-0045972; Japanese patent publication number Hei 2009-69607; and Japanese patent publication number Hei 2008-225461).
The present invention is directed to a melted connection method. The optical fiber connector using the above mentioned melted connection method, as shown in FIG. 1, comprises a ferrule 1 including a ferrule optical fiber, an elastic member 2 elastically supporting the ferrule, a plug frame 4 accommodating the ferrule and the elastic member, a stopper 3 installed at the plug frame and fixing the ferrule and the elastic member at the plug frame, a reinforcing sleeve 5 configured to reinforce the ends of the ferrule optical fiber and the melted connection part of the ends of the main optical fiber, a plug handle 6 and a boot 7.
The optical fiber connector of the melted connection method features in that the ferrule is elastically supported by the elastic member, and the elastic member 2 moves within an allowed movement range. In the event that the ferrule moves within a range that the elastic member allows, the adhered state between the ferrule body 1a and the ferrule optical fiber 1b might be damaged or the ferrule optical fiber might become short circuit, and a ferrule optical fiber portion 1b′ might be bent.
As shown in FIG. 1b, when the ferrule moves within the range that the elastic member 2 allows when an external force is applied, the portion 2b′ of the ferrule optical fiber 1b between the ferrule body 1a and the reinforcing sleeve 7 is bent, and the frequent movements of the ferrule body 1a makes defective the adhered state between the ferrule body and the ferrule optical fiber, and the ferrule optical fiber might become short circuit. When the external force is applied to the ferrule body 1a, part of the ferrule optical fiber is bent, and part of the short ferrule optical fiber is bent, which means that the bent angle is great, so the efficiency of the optical fiber is lowered.
In the optical fiber connector of the conventional melted connection method, when the melted connection part is reinforced by heating the reinforcing sleeve formed of the shrinkable tube, the deformation might occur as the adhesive used so as to integrally connect the ferrule body and the ferrule optical fiber melts, so when assembling the optical fiber connector, it is needed to minimize exposure of the ferrule to heat.
As the exposure of the ferrule to heat is minimized, a cold peeling (room temperature) is mainly performed when peeling the coating of the ferrule optical fiber. At this time, a greater force (load) is applied to the ferrule when peeling the coating of the ferrule optical fiber, so the adhered portion of the ferrule is damaged, and the ferrule optical fiber may short circuit (disconnection).
The problems of the conventional art will be described with reference to the above-mentioned patent documents.
The optical fiber connector disclosed in Korean patent publication number 10-2009-0083373 is directed to a compact size. The structural ferule 7 and the reinforcing (sleeve) sleeve 15 are arranged closer to each other, so the adhesive used for integrally connecting the optical fiber to the ferule might be deformed by the heat when heating for the sake of the heat shrinkage of the reinforcing (arc) sleeve.
The optical fiber connector disclosed in Japanese patent publication number Hei 2008-225461 is directed to forming a protruded portion at the fixture engaged to the frame while making sure that the tensional force is enhanced so that it can integrally engage when the reinforcing sleeve is thermally contracted. When the reinforcing sleeve is thermally contracted and is integrally formed at the protruded portion of the structural fixture, the fixture and the optical fiber of the ferrule are integrated by the reinforcing sleeve. As shown in FIG. 1, when the force (load) is applied to the front ferrule of the connector, the ferrule moves in a longitudinal direction of the optical fiber by means of the elastic member. At this time, as shown in FIG. 1b, the portion 1b′ of the ferrule optical fiber 1b having a short length is bent (curved), so the optical fiber might be cut resulting in a short circuit or it might be bent at a great angle, so the loss ratio might be greatly increased.
The optical fiber connectors of Korean patent publication number 10-2009-0083373; Japanese patent publication number Hei 2009-69607; Japanese patent publication number Hei 2008-225461 have features in that the optical fiber is peeled at the factory and is assembled to the ferrule using the adhesive and is cut and supplied to the on-site location. If it is supplied with the coating unpeeled, the ferrule optical fiber made by adhering the ferrule and the optical fiber using an adhesive might have a weakened strength at the adhered portion due to the peeling load when peeling at the on-site location, so it is impossible to overcome the deformation and short circuit problems.
As the optical fibers are peeled, adhered, cut and supplied to the on-site location for the sake of the ferrule in the factory, it is hard to handle which results in the increased manufacture cost, and the short circuit might occur during the handing at the on-site location.
In addition, the peeled optical fibers are exposed long in the air, so they might be contaminated by moisture or other contaminants.
As a method for improving the above mentioned problems, Japanese patent publication number Hei 2009-69607 provides a packing technology so as to provide the peeled optical fiber of the ferrule. In the event that they are packed and supplied, the manufacture cost might be increased, and the whole volume of the packed product increases, so the costs needed for the transportation increases.
The reinforcing sleeve 5 as shown in FIG. 2 is adapted to the conventional optical fiber connector and comprises a dual tube formed of two thermal shrinkage tubes of an outer tube 5a and an inner tube 5b and a metallic reinforcing pin 5c, so the thermal shrinkage takes long due to the dual tube during the heating for the sake of thermal shrinkage.
In order to improve the above mentioned problems, the applicant of the is present application provided the optical fiber connector of Korean registration number 10-1038195 and the optical fiber connector made by the assembling method of the same as shown in FIG. 3.
In case of the optical fiber connector of the patent registration number 10-1038195, the ferrule can move in the longitudinal direction of the optical fiber when an external force is applied by means of the elastic member, so the reinforcing sleeve configured to reinforce the melted connection part might be bent. The optical fiber connector of the patent registration number 10-1038195, as shown in FIG. 1, can improve the problems that the cut losses and the increased loss ratio increase as it is bent at a great angle; however as the reinforcing sleeve is frequently bent, the cut losses or the increased loss ratio still occur.